import {VantComponent} from '../common/component'
import {touch} from '../mixins/touch'
import {getAllRect, getRect, groupSetData, nextTick, requestAnimationFrame,} from '../common/utils'
import {isDef} from '../common/validator'
import {useChildren} from '../common/relation'

VantComponent({
  mixins: [touch],
  classes: [
    'nav-class',
    'tab-class',
    'tab-active-class',
    'line-class',
    'wrap-class',
  ],
  relation: useChildren('tab', function () {
    this.updateTabs()
  }),
  props: {
    sticky: Boolean,
    border: Boolean,
    swipeable: Boolean,
    titleActiveColor: String,
    titleInactiveColor: String,
    color: String,
    animated: {
      type: Boolean,
      observer() {
        this.children.forEach((child, index) => child.updateRender(index === this.data.currentIndex, this))
      },
    },
    lineWidth: {
      type: null,
      value: 40,
      observer: 'resize',
    },
    lineHeight: {
      type: null,
      value: -1,
    },
    active: {
      type: null,
      value: 0,
      observer(name) {
        if (name !== this.getCurrentName()) {
          this.setCurrentIndexByName(name)
        }
      },
    },
    type: {
      type: String,
      value: 'line',
    },
    ellipsis: {
      type: Boolean,
      value: true,
    },
    duration: {
      type: Number,
      value: 0.3,
    },
    zIndex: {
      type: Number,
      value: 1,
    },
    swipeThreshold: {
      type: Number,
      value: 5,
      observer(value) {
        this.setData({
          scrollable: this.children.length > value || !this.data.ellipsis,
        })
      },
    },
    offsetTop: {
      type: Number,
      value: 0,
    },
    lazyRender: {
      type: Boolean,
      value: true,
    },
    useBeforeChange: {
      type: Boolean,
      value: false,
    },
  },
  data: {
    tabs: [],
    scrollLeft: 0,
    scrollable: false,
    currentIndex: 0,
    container: null,
    skipTransition: true,
    scrollWithAnimation: false,
    lineOffsetLeft: 0,
    inited: false,
  },
  mounted() {
    requestAnimationFrame(() => {
      this.swiping = true
      this.setData({
        container: () => this.createSelectorQuery().select('.van-tabs'),
      })
      this.resize()
      this.scrollIntoView()
    })
  },
  methods: {
    updateTabs() {
      const {children = [], data} = this
      this.setData({
        tabs: children.map((child) => child.data),
        scrollable: this.children.length > data.swipeThreshold || !data.ellipsis,
      })
      this.setCurrentIndexByName(data.active || this.getCurrentName())
    },
    trigger(eventName, child) {
      const {currentIndex} = this.data
      const data = this.getChildData(currentIndex, child)
      if (!isDef(data)) {
        return
      }
      this.$emit(eventName, data)
    },
    onTap(event) {
      const {index} = event.currentTarget.dataset
      const child = this.children[index]
      if (child.data.disabled) {
        this.trigger('disabled', child)
        return
      }
      this.onBeforeChange(index).then(() => {
        this.setCurrentIndex(index)
        nextTick(() => {
          this.trigger('click')
        })
      })
    },
    // correct the index of active tab
    setCurrentIndexByName(name) {
      const {children = []} = this
      const matched = children.filter((child) => child.getComputedName() === name)
      if (matched.length) {
        this.setCurrentIndex(matched[0].index)
      }
    },
    setCurrentIndex(currentIndex) {
      const {data, children = []} = this
      if (!isDef(currentIndex) ||
        currentIndex >= children.length ||
        currentIndex < 0) {
        return
      }
      groupSetData(this, () => {
        children.forEach((item, index) => {
          const active = index === currentIndex
          if (active !== item.data.active || !item.inited) {
            item.updateRender(active, this)
          }
        })
      })
      if (currentIndex === data.currentIndex) {
        if (!data.inited) {
          this.resize()
        }
        return
      }
      const shouldEmitChange = data.currentIndex !== null
      this.setData({currentIndex})
      requestAnimationFrame(() => {
        this.resize()
        this.scrollIntoView()
      })
      nextTick(() => {
        this.trigger('input')
        if (shouldEmitChange) {
          this.trigger('change')
        }
      })
    },
    getCurrentName() {
      const activeTab = this.children[this.data.currentIndex]
      if (activeTab) {
        return activeTab.getComputedName()
      }
    },
    resize() {
      if (this.data.type !== 'line') {
        return
      }
      const {currentIndex, ellipsis, skipTransition} = this.data
      Promise.all([
        getAllRect(this, '.van-tab'),
        getRect(this, '.van-tabs__line'),
      ]).then(([rects = [], lineRect]) => {
        const rect = rects[currentIndex]
        if (rect == null) {
          return
        }
        let lineOffsetLeft = rects
          .slice(0, currentIndex)
          .reduce((prev, curr) => prev + curr.width, 0)
        lineOffsetLeft +=
          (rect.width - lineRect.width) / 2 + (ellipsis ? 0 : 8)
        this.setData({lineOffsetLeft, inited: true})
        this.swiping = true
        if (skipTransition) {
          // waiting transition end
          setTimeout(() => {
            this.setData({skipTransition: false})
          }, this.data.duration)
        }
      })
    },
    // scroll active tab into view
    scrollIntoView() {
      const {currentIndex, scrollable, scrollWithAnimation} = this.data
      if (!scrollable) {
        return
      }
      Promise.all([
        getAllRect(this, '.van-tab'),
        getRect(this, '.van-tabs__nav'),
      ]).then(([tabRects, navRect]) => {
        const tabRect = tabRects[currentIndex]
        const offsetLeft = tabRects
          .slice(0, currentIndex)
          .reduce((prev, curr) => prev + curr.width, 0)
        this.setData({
          scrollLeft: offsetLeft - (navRect.width - tabRect.width) / 2,
        })
        if (!scrollWithAnimation) {
          nextTick(() => {
            this.setData({scrollWithAnimation: true})
          })
        }
      })
    },
    onTouchScroll(event) {
      this.$emit('scroll', event.detail)
    },
    onTouchStart(event) {
      if (!this.data.swipeable)
        return
      this.swiping = true
      this.touchStart(event)
    },
    onTouchMove(event) {
      if (!this.data.swipeable || !this.swiping)
        return
      this.touchMove(event)
    },
    // watch swipe touch end
    onTouchEnd() {
      if (!this.data.swipeable || !this.swiping)
        return
      const {direction, deltaX, offsetX} = this
      const minSwipeDistance = 50
      if (direction === 'horizontal' && offsetX >= minSwipeDistance) {
        const index = this.getAvaiableTab(deltaX)
        if (index !== -1) {
          this.onBeforeChange(index).then(() => this.setCurrentIndex(index))
        }
      }
      this.swiping = false
    },
    getAvaiableTab(direction) {
      const {tabs, currentIndex} = this.data
      const step = direction > 0 ? -1 : 1
      for (let i = step; currentIndex + i < tabs.length && currentIndex + i >= 0; i += step) {
        const index = currentIndex + i
        if (index >= 0 &&
          index < tabs.length &&
          tabs[index] &&
          !tabs[index].disabled) {
          return index
        }
      }
      return -1
    },
    onBeforeChange(index) {
      const {useBeforeChange} = this.data
      if (!useBeforeChange) {
        return Promise.resolve()
      }
      return new Promise((resolve, reject) => {
        this.$emit('before-change', Object.assign(Object.assign({}, this.getChildData(index)), {callback: (status) => (status ? resolve() : reject())}))
      })
    },
    getChildData(index, child) {
      const currentChild = child || this.children[index]
      if (!isDef(currentChild)) {
        return
      }
      return {
        index: currentChild.index,
        name: currentChild.getComputedName(),
        title: currentChild.data.title,
      }
    },
  },
})
